Oscillator Scheme Research Articles

Continuous-variable quantum key distribution robust against environmental disturbances.

Continuous variable quantum key distribution (CV-QKD) can guarantee that two parties share secure keys even in the presence of an eavesdropper. However, the polarization direction of the coherent state transmitted in CV-QKD is susceptible to environmental disturbances during channel transmission, making it difficult to share keys consistently over long periods of time. Therefore, a CV-QKD system that can resist environmental disturbance is very urgent. In this paper, we propose a new optical architecture for CV-QKD based on the Faraday-Michelson interference (FMI) structure, and finally form an all-single-mode (SM) fiber-based stable CV-QKD system which employs transmitted local oscillator (TLO) scheme and discrete modulation coherent state (DMCS) protocol. Specifically, since the Faraday mirror rotates the polarization direction of light by 90o, the birefringence effect of light can be effectively dealt with, thus ensuring the same polarization state of light before and after reflection. The final simulation results show that the theoretical secret key rate of this scheme can reach 139 kbps at 70 km, which can further improve the stability and robustness of CV-QKD in the real environment, and provide technical support for the next-generation high-stability QKD system.

Optical frequency divider: Capable of measuring optical frequency ratio in 22 digits

Recent advances in optical frequency standards and optical frequency combs (OFCs) have drawn wide attention since by transforming other quantities into frequency metrology, a higher measurement sensitivity or accuracy can be achieved. Among them, the search for dark matter, tests of relativity, and detection of gravitational wave anticipate even more precise frequency ratio measurement of optical signals, which challenges the state-of-the-art optical frequency standards and OFCs. Here, we report an optical frequency divider (OFD) based on a Ti:sapphire mode-locked laser, which can realize ultraprecise optical frequency ratio measurements and optical frequency division to other desired frequencies. The OFD is based on an OFC frequency-stabilized to a hydrogen maser, whose frequency noise in optical frequency division is subtracted via the transfer oscillator scheme. An optically referenced radio frequency time-base is introduced for the fine-tuning of the divisor and the reduction in division noise. Using the OFD, the frequency ratio between the fundamental and its second harmonic of a 1064 nm laser is measured with a fractional uncertainty of 3 × 10−22, nearly five times better than previous results. Meanwhile, we also report the ability to transport between laboratories, the long-term operation, and the multi-channel division of the OFD.

Simultaneous BPSK classical communication and continuous variable quantum key distribution with a locally local oscillator regenerated by optical injection phase locked loop

This paper proposes a scheme for simultaneous classical communication and continuous variable quantum key distribution with a true local oscillator. In this scheme, the emitter’s laser, after binary phase-shift keying (BPSK) modulation, is multiplexed in polarization with the quantum signal and sent to the receiver. After BPSK demodulation and correction, this signal is used for local oscillator regeneration by an optical injection phase-locked loop method. Comparing the effective noise sources in this scheme with typical local local oscillator schemes revealed that continuous variable quantum key distribution (CV-QKD) with a true local oscillator based on the optical injection phase-locked loop encounters lower levels of noise in comparison to the pre-existing genuine local oscillator CV-QKDs.

Inaccessibility regions for the sterile neutrino searches at the long baseline experiments

We provide a novel approach based on χ2 analysis that investigates regions in the neutrino parameter space where long baseline experiments cannot discriminate between the (3+1)ν oscillation scheme and the standard 3ν oscillation scheme. We call such region of parameter space “the inaccessible region”. The inaccessible area of parameter space is so named because the minimal value of χ2 remains almost unaltered even after inserting the sterile neutrino in the description of the neutrino oscillation data. Such inaccessible zones are discovered for the three long-baseline experiments (T2K, NOva and DUNE). Finally, we find the region of the sterile neutrino parameter space that remains inaccessible even after combining all three experiments. If sterile neutrinos exist in nature but their mixing parameters are in this range, these long-baseline experiments cannot prove their existence. The significance of our finding stems from the likelihood of sterile neutrinos existing in the accessible zone, which may be tested in these experiments in near future.

Nonlinear spectral compression in high-power narrow-linewidth polarization maintaining fiber amplifiers for SBS suppression.

In this paper, we propose a method for narrowing the spectrum in high-power narrow-linewidth polarization-maintaining (PM) fiber amplifiers and investigate its potential for suppressing the stimulated Brillouin scattering (SBS). In this method, in addition to common phase modulation to suppress SBS, precisely designed amplitude modulation is induced to generate self-phase modulation in a high-power PM fiber amplifier. In this co-modulation way, the spectrum can be gradually compressed along the fiber. Compared to phase modulation alone or fiber-Bragg-gratings (FBGs) based narrow-linewidth fiber oscillator schemes, in which the spectrum remains the same or broadens, this scheme can achieve a higher SBS threshold for the same output spectral linewidth. Experiments on a ∼ 3 kW peak power quasi-continuous wave (QCW) fiber amplifier show that the co-modulation scheme can compress the spectrum from 0.25 nm to 0.084 nm as output peak power increases from 13 W to 3.2 kW and enhances the SBS threshold by ∼1.7 times compared to traditional FBGs-based fiber oscillator schemes, and by ∼1.4 times compared to common phase modulation schemes. This co-modulation scheme has the potential for mitigating SBS in high-power fiber amplifiers.

Automatic Balancing of “Arbiter” Physical Unclonable Function Paths

The features of building on the basis of programmable logic integrated circuits of “arbiter” physical unclonable functions (APUF) are considered. The problem of asymmetry of pairs of APUF paths is indicated and the negative impact of this phenomenon on their characteristics is noted. A time measuring system based on a ring oscillator scheme, which is used to analyze the time characteristics of APUF paths, is described. A method for automatic balancing of signal propagation delays through the APUF paths based on the calculation of the corrective value is proposed. The consistency of the proposed balancing technique is experimentally confirmed based on the improvement in the characteristics of the APUF after its implementation. A digital scheme of this technique is presented, which can form the basis for the development of a delay auto correction scheme through APUF paths with different levels of autonomy.

Dual-Wavelength Mode-Locked Oscillation with Graphene Nanoplatelet Saturable Absorber in Erbium-Doped Fiber Laser

In this work, we demonstrate a dual-wavelength passively mode-locked erbium-doped fiber laser employing graphene nanoplatelet as saturable absorber. The dual-wavelength laser is generated in ~1530 nm and ~1550 nm wavelength regions by splitting the main signal into two separate laser oscillations via a red/blue wavelength division multiplexer. Both the unidirectional and bidirectional dual-wavelength oscillation scheme are investigated, and it is found that the latter is advantageous in providing narrower pulse widths of 890 fs and 980 fs for the respective wavelength region, on top of boosting the pulse energy to the maximum value of 139 pJ and 155 pJ, respectively. It is believed that the bidirectional dual-wavelength oscillation scheme can minimize the overlapping effect between the neighboring pulses that cause pulse distortion as well as signal attenuation compared with unidirectional dual-wavelength oscillation. This work expands the dynamics of cavity structure design for synchronized dual-wavelength mode-locked fiber laser generation.

Pulse Frequency Modulation for Parity-Time-Symmetric Wireless Power Transfer System

This article proposes and implements an advanced pulse frequency modulation (PFM) scheme to adjust the output power of the parity-time (PT) symmetric wireless power transfer (WPT) system. The key is to utilize PFM to adjust the duty ratio of the self-excited oscillating inverter for the PT-symmetric WPT system, hence transferring more power than that of the conventional forced oscillating inverter under the same input voltage and duty ratio. Besides, the transmission efficiency can maintain high when the coupling coefficient is larger than the critical value. With a proper signal processing circuit, the phase of the inverter output voltage can lead to that of the primary-side current, which can help reduce the switching loss. Therefore, the system efficiency of this self-excited oscillation scheme for WPT can keep high, while the output power can be larger than that of using the conventional forced oscillation scheme. Theoretical analysis and simulation results are given to verify the feasibility of the proposed scheme.

QID: Robust Mobile Device Recognition via a Multi-Coil Qi-Wireless Charging System

Recent years have witnessed the increasing penetration of wireless charging base stations in the workplace and public areas, such as airports and cafeterias. Such an emerging wireless charging infrastructure has presented opportunities for new indoor localization and identification services for mobile users. In this paper, we present QID, the first system that can identify a Qi-compliant mobile device during wireless charging in real-time. QID extracts features from the clock oscillator and control scheme of the power receiver and employs light-weight algorithms to classify the device. QID adopts a 2-dimensional motion unit to emulate a variety of multi-coil designs of Qi, which allows for fine-grained device fingerprinting. Our results show that QID achieves high recognition accuracy. With the prevalence of public wireless charging stations, our results also have important implications for mobile user privacy.

Numerical investigation of the fiber optic parametric oscillator scheme with a dual-arm synchronous pumping

Numerical investigation of the fiber optic parametric oscillator scheme with a dual-arm synchronous pumping

Optical injection locking assisted all-optical microwave oscillator

This paper reports an optical injection locking (OIL) assisted all-optical microwave oscillator (AOMO) scheme for the photonic generation of a microwave (MW) signal and demonstrates a 40th harmonic single-mode signal generation with an external low-frequency radio-frequency (RF) signal. In this all-optical single-loop oscillator that only depends on optical devices, the stimulated Brillouin scattering (SBS) effect of a coil of single-mode fiber (SMF) and a semiconductor optical amplifier (SOA) are used to select the oscillation frequency and modulate the optical feedback signal, respectively. The OIL effect in a distributed feedback (DFB) laser multiplies the frequency of the external RF signal. Thanks to the OIL module, it only requires an optical loop to acquire a single-mode oscillation and the oscillation signal is phase-related to the low-frequency RF source. The experiment demonstrates the generation of a single-mode MW signal of 10.71 GHz with an external RF signal of 267.8 MHz, with a frequency multiplication factor of 40. Mode-hopping is not evident in the output signal, and a moderately low-quality OIL signal is acceptable since unwanted harmonics and the phase noise floor of the OIL signal have little impact on the generated MW signal.

Dependence of the Piezoelectric Micropump Operating Mode on Its Geometry

A mathematical and computer axisymmetric models in which periodic oscillations of ring piezoelectric actuators placed on an elastic tube of circular cross-section leads to radial deformations of the tube is constructed. The result of these displacements is a local compression of the microchannel, which leads to changes in its volume and the corresponding pushing of the fluid. If a non-symmetrical oscillation scheme is used, the average fluid flow over the period will be non-zero and the device can be used as a micropump. The aim of the work is a computer study of the geometric features of an axisymmetric piezoelectric micropump, taking into account the processes of heat transfer by a fluid in the channel. The dependence of the average fluid flow rate on the channel parameters and the frequency of oscillations of the piezoelectric actuators is determined by the method of factorial experiment. The parameters preventing heat backflow have been determinate, which makes it possible to use a device for supplying coolant to a microgripper cooling system.

Stable and Tunable Optoelectronic Oscillator With External Stimulated Brillouin Beat Note Injection

Broadband and tunable microwave signals are widely used in modern communication systems and sensing systems. In this work, we demonstrate a stable and tunable optoelectronic oscillator (OEO) scheme based on external low-power beat note injection of the stimulated Brillouin signal and a phase modulation sideband of the original pump signal. The injection-locked system reduces the high-frequency disturbance induced by the beat note signal, and thus the power required only meets the OEO locking threshold requirement. In addition, the external stimulated Brillouin signal generator avoids the excessive length of the resonant cavity and guarantees the frequency stability, especially the mode stability in the OEO with a total path length of ~12 m. By varying the stimulated Brillouin signal frequency and selecting different pump modulation sidebands, a continuously tuned beat note is generated, and a beat note injected OEO with a maximum frequency up to 11.5 GHz is achieved, which is the intrinsic upper frequency limit of the devices used, even for an injection beat frequency power as low as -14 dBm ( ~ 40 μ W). Our work provides an important solution for the realization of widely tunable microwave systems.

A Tunable-Gain Transimpedance Amplifier for CMOS-MEMS Resonators Characterization.

CMOS-MEMS resonators have become a promising solution thanks to their miniaturization and on-chip integration capabilities. However, using a CMOS technology to fabricate microelectromechanical system (MEMS) devices limits the electromechanical performance otherwise achieved by specific technologies, requiring a challenging readout circuitry. This paper presents a transimpedance amplifier (TIA) fabricated using a commercial 0.35-µm CMOS technology specifically oriented to drive and sense monolithically integrated CMOS-MEMS resonators up to 50 MHz with a tunable transimpedance gain ranging from 112 dB to 121 dB. The output voltage noise is as low as 225 nV/Hz1/2—input-referred current noise of 192 fA/Hz1/2—at 10 MHz, and the power consumption is kept below 1-mW. In addition, the TIA amplifier exhibits an open-loop gain independent of the parasitic input capacitance—mostly associated with the MEMS layout—representing an advantage in MEMS testing compared to other alternatives such as Pierce oscillator schemes. The work presented includes the characterization of three types of MEMS resonators that have been fabricated and experimentally characterized both in open-loop and self-sustained configurations using the integrated TIA amplifier. The experimental characterization includes an accurate extraction of the electromechanical parameters for the three fabricated structures that enables an accurate MEMS-CMOS circuitry co-design.

High energy mid-infrared laser pulse output from a BaGa4Se7 crystal-based optical parametric oscillator.

We report a high energy, narrow spectral linewidth mid-infrared laser pulse output from a Nd:Y3Al5O12 laser-pumped BaGa4Se7 (BGSe) crystal-based optical parametric oscillator (OPO). Output pulse energy of 21.5 mJ was obtained at 3816 nm, with spectral width of 12 nm and pulse width of 11.4 ns, corresponding to peak power as high as 1.89 MW. A BGSe crystal with aperture size of 10mm×10mm and length of 16 mm was applied as the nonlinear crystal in a pump fed back OPO for achieving such high pulse energy output from the simple oscillator scheme.

A 56-to-66 GHz CMOS Low-Power Phased-Array Receiver Front-End With Hybrid Phase Shifting Scheme

This paper presents a millimeter-wave phased-array receiver front-end with compact size and low-power consumption. A combination of local oscillator (LO) and radio frequency (RF) phase-shifting schemes is used to reduce the power consumption and RF path loss. Moreover, in the implementation of active circuits, a bulk isolation technique is used to achieve a higher power gain with a minimum number of stages. This technique is also utilized in the RF path phase shifter switches to mitigate the loss. To validate the proposed architecture, a single-element 56-to-66 GHz phased-array receiver front-end is fabricated in a 65-nm bulk CMOS process. Based on the measurement results, the receiver achieves a power gain of ~14.85 dB and a minimum noise figure (NF) of 5.7 dB. The measured average RMS phase and gain errors are ~3.5° and ~0.45 dB, respectively. The input 1-dB compression point ( $\text{P}_{\mathrm {-1dB}}$ ) of the receiver chain is about −19 dBm. The complete receiver, including active balun and required buffers (excluding the LO), consumes ~50 mW from a 1-V power supply and excluding the pads occupies a silicon area of 0.93 mm2.

Performance of continuous variable quantum key distribution system at different detector bandwidth

We evaluate the performance of Gaussian Modulated Coherent State (GMCS) Continuous-Variable Quantum Key Distribution (CV-QKD), in terms of secure key rate, at different detector bandwidths. We illustrate the advantages and limitations of high-speed CV-QKD systems using a general noise model in which we consider various noise sources and their dependence upon detection bandwidth. Experimentally, the feasibility of high speed CV-QKD is demonstrated by using a GHz bandwidth balanced homodyne detector (BHD) established with commercially available components. We provide secure key rates of transmitted and local local oscillator schemes under various clock rates.

Frequency-definable linearly chirped microwave waveform generation by a Fourier domain mode locking optoelectronic oscillator based on stimulated Brillouin scattering.

A Fourier domain mode locking (FDML) optoelectronic oscillator (OEO) scheme based on stimulated Brillouin scattering (SBS) is proposed to generate linearly chirped microwave waveforms (LCMWs) with excellent frequency sweep linearity and a precisely controllable frequency sweep range. The kernel of the proposed scheme is a center-frequency-definable SBS-based fast-tunable microwave photonic bandpass filter based on frequency-selective phase-to-intensity conversion, which is realized by using a single laser source to generate a fast frequency-swept probe light and a tunable pump light via electro-optic frequency shifting. A proof-of-concept experiment is carried out to demonstrate the proposed scheme, where LCMWs with flexibly-tunable center frequency and bandwidth are generated. In the experiment, the maximum time-bandwidth product and chirp rate are 82000 and 0.195 GHz/µs, respectively. Most importantly, the frequency deviation is less than 1 MHz and the frequency sweep linearity is smaller than 1.7%, which indicate that the proposed SBS-based FDML OEO can generate frequency-definable LCMWs with excellent frequency sweep linearity.

New oscillator concept based on band edge degeneracy in lumped double‐ladder circuits

An oscillator scheme based on the degenerate band edge (DBE) in a periodic, double-ladder resonant circuit made of lumped elements is proposed for the first time. The circuit exhibits a DBE in the dispersion diagram of its phase-frequency eigenstates and possesses unique resonance features associated with a high loaded Q-factor resonance, compared to a single-ladder circuit. This oscillator is shown to have an oscillation threshold that is half that of a single LC ladder circuit having the same total quality factor, and thus is more robust than an LC oscillator in the presence of losses. Moreover, the double-ladder oscillators have a unique mode selection scheme that leads to stable single-frequency oscillations even when the load is varied. It is also shown that the output amplitude of the double-ladder oscillator is much less sensitive to the output loading compared to single-ladder oscillators. The authors show the analysis and design of such oscillators that potentially lead to enhancing the efficiency of RF components and sources.

Low phase noise optoelectronic oscillator based on an electroabsorption modulated laser

An optoelectronic oscillator (OEO) scheme based on an electroabsorption modulated laser (EML) is proposed and experimentally demonstrated. The oscillation conditions and a complete phase noise model for the EML-based OEO are detailed. A 20-GHz microwave signal with a side-mode suppression ratio of 42dB is generated and evaluated. The corresponding single sideband phase noise with a 1-km and 4-km fiber used in the loop is respectively measured to be -110.2 dBc/Hz and -114.8 dBc/Hz at 10kHz offset frequency. The experimental phase noise results agree well with the theoretical results in an offset frequency range from 100Hz to 10MHz.